A variety of micropuncture studies are proposed in an effort to further elucidate kidney function in health and disease. Rats and other laboratory animals with normal kidneys and with various models of experimental kidney disease will be employed in a variety of studies of renal tubular transport processes and their control mechanisms. Amongst specific projects underway are studies of the effect of increased intrarenal pressure on renal tubular permeability. Clearance and micropuncture studies are underway in rats with experimental glomerulonephritis. Studies include whole kidney clearance studies and micropuncture measurements. In addition to studies of tubular transport,studies of glomerulohydrodynamics are in progress, as well as the response to plasma volume expansion with hyperoncotic albumin solution. The intrarenal mechanisms leading to salt retention and edema formation in rats with experimental heart failure are also being studied.